The present invention relates to a front-wheel driving mechanism in a four-wheel drive tractor provided with a front-wheel driving mechanism.
The prior art relating to a structure which drives the front wheels in a four-wheel drive tractor discloses a structure wherein a plurality of bevel gears are assembled around the outer circumference of a kingpin and power is transmitted to the front wheels through the meshed bevel gears or other structure and from the meshed gears through a universal joint forming a portion of a front-wheel driving shaft system. In such a tractor provided with a structure which drives both the front and rear wheels, the driving force is significantly increased but the turning ability is significantly reduced in comparison with a two-wheel drive tractor which drives the rear wheels only. In the two above described structures, the turning range is significantly limited on account of the presence of the bevel gears and the universal joint housing. As a result, although a prior art two-wheel tractor which drives only the rear wheels can be turned at a turning angle of nearly 65 degrees, a tractor provided with a front-wheel driving mechanism can be turned at an angle of only 45 degrees at the most. When a tractor having a small turning angle is used on the farm where sharp turning angles are particularly required, the usefulness and safety are significantly hindered. Therefore an improvement in this type of tractor has long been desired.